Semiconductor light emitting element and method for manufacturing same

ABSTRACT

According to one embodiment, a semiconductor light emitting element includes: a support substrate; a bonding layer provided on the support substrate; an LED layer provided on the bonding layer; and a buffer layer softer than the bonding layer. The buffer layer is placed in one of between the support substrate and the bonding layer and between the bonding layer and the LED layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior U.S. Provisional Patent Application 61/580,729, filed on Dec.28, 2011; the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a semiconductor lightemitting element and method for manufacturing same.

BACKGROUND

In manufacturing a thin film LED (light emitting diode), a bonding layermade of e.g. gold alloy is formed on a support substrate. On the otherhand, on a crystal growth substrate, an LED layer and a reflection layerare formed, and a bonding layer made of e.g. gold alloy is formedthereon. Then, the bonding layers are bonded to each other to place theLED layer on the support substrate. Subsequently, dicing is performedfor division into elements.

However, in this method, the bonding layers after bonding are hardened.Thus, at the time of dicing, peeling may occur at the interface of oneof the layers. This decreases the yield of LED.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a semiconductor light emittingelement according to a first embodiment;

FIGS. 2A to 2C, FIGS. 3A and 3B, and FIG. 4 are process sectional viewsillustrating the method for manufacturing a semiconductor light emittingelement according to the first embodiment;

FIG. 5 is a sectional view illustrating a semiconductor light emittingelement according to a second embodiment;

FIGS. 6A to 6C are process sectional views illustrating the method formanufacturing a semiconductor light emitting element according to thesecond embodiment;

FIG. 7 is a sectional view illustrating a semiconductor light emittingelement according to a third embodiment;

FIG. 8 is a sectional view illustrating a semiconductor light emittingelement according to a fourth embodiment;

FIG. 9 is a sectional view illustrating a semiconductor light emittingelement according to a fifth embodiment;

FIG. 10 is a sectional view illustrating a semiconductor light emittingelement according to a comparative example; and

FIG. 11 illustrates a method for manufacturing a semiconductor lightemitting element according to the comparative example.

DETAILED DESCRIPTION

In general, according to one embodiment, a semiconductor light emittingelement includes: a support substrate; a bonding layer provided on thesupport substrate; an LED layer provided on the bonding layer; and abuffer layer softer than the bonding layer. The buffer layer is placedin one of between the support substrate and the bonding layer andbetween the bonding layer and the LED layer.

Embodiments will now be described with reference to the drawings.

First, a first embodiment of the invention is described.

FIG. 1 is a sectional view illustrating a semiconductor light emittingelement according to this embodiment.

The semiconductor light emitting element according to this embodiment isa thin film LED.

As shown in FIG. 1, the semiconductor light emitting element 1 accordingto this embodiment includes a support substrate 10 made of e.g. singlecrystal silicon (Si). On the support substrate 10, a barrier layer 11 isprovided. The barrier layer 11 is e.g. a Ti/Pt/Ti three-layer film inwhich a titanium (Ti) layer 21, a platinum (Pt) layer 22, and a titanium(Ti) layer 23 are stacked in this order.

On the barrier layer 11, a bonding layer 12 is provided. The bondinglayer 12 is formed from e.g. gold-indium (Au—In) alloy. The thickness ofthe bonding layer 12 is e.g. approximately 1-5 μm. On the bonding layer12, a barrier layer 13 is provided. The barrier layer 13 is a Ti/Pt/Tithree-layer film similar to the barrier layer 11.

On the barrier layer 13, a buffer layer 14 is provided. The buffer layer14 is softer than the bonding layer 12. For instance, the Young'smodulus of the material forming the buffer layer 14 is lower than theYoung's modulus of the material forming the bonding layer 12. The bufferlayer 14 is formed from a material including gold (Au), such as puregold. The thickness of the buffer layer 14 is e.g. 0.1-1 μm, such as 0.4μm.

On the buffer layer 14, a barrier layer 15 is provided. Theconfiguration of the barrier layer 15 is similar to that of the barrierlayer 11. On the barrier layer 15, a reflection layer 16 is provided.The reflection layer 16 is made of a material including silver (Ag),such as pure silver. Alternatively, the reflection layer 16 may beformed from aluminum (Al).

On the reflection layer 16, an LED layer 17 is provided. The LED layer17 is a layer for emitting light under supply of electrical power. Inthe LED layer 17, sequentially from the support substrate 10 side, ap-type layer 25, a light emitting layer 26, and an n-type layer 27 arestacked. The structure of the LED layer 17 is e.g. a quaternary MQW(multiple quantum well) structure of indium-aluminum-gallium-phosphorus(InAlGaP).

On part of the LED layer 17, an upper electrode layer 18 is provided. Onthe entire lower surface of the support substrate 10, a lower electrodelayer 19 is provided.

The barrier layer 11 is a layer for suppressing reaction between thesupport substrate 10 and the bonding layer 12. The barrier layer 13 is alayer for suppressing reaction between the bonding layer 12 and thebuffer layer 14. The barrier layer 15 is a layer for suppressingreaction between the buffer layer 14 and the reflection layer 16. Here,each barrier layer may be formed from a layer including nickel (Ni). Thereflection layer 16 is a layer for causing the light emitted downwardfrom the LED layer 17 to be reflected upward.

Next, a method for manufacturing a semiconductor light emitting elementaccording to this embodiment is described.

FIGS. 2A to 2C, FIGS. 3A and 3B, and FIG. 4 are process sectional viewsillustrating the method for manufacturing a semiconductor light emittingelement according to this embodiment.

First, as shown in FIG. 2A, a support substrate 10 is prepared. As thesupport substrate 10, for instance, a silicon wafer is used. Then, onthe support substrate 10, a titanium layer 21 (see FIG. 1), a platinumlayer 22 (see FIG. 1), and a titanium layer 23 (see FIG. 1) aredeposited in this order to form a barrier layer 11. Next, a materialincluding gold, such as pure gold, is deposited to form a bonding layer31 on the barrier layer 11. The thickness of the bonding layer 31 is setto approximately half the thickness of the bonding layer 12 (see FIG. 1)in the completed semiconductor light emitting element 1. Thus, a supportmember 41 with the barrier layer 11 and the bonding layer 31 stacked onthe support substrate 10 is fabricated.

On the other hand, as shown in FIG. 2B, a crystal growth substrate 30 isprepared. As the crystal growth substrate 30, for instance, a singlecrystal gallium arsenide (GaAs) substrate is used. Then, on the crystalgrowth substrate 30, an n-type layer 27 (see FIG. 1), a light emittinglayer 26 (see FIG. 1), and a p-type layer 25 (see FIG. 1) areepitaxially grown in this order to form an LED layer 17.

Next, silver, for instance, is deposited to form a reflection layer 16on the LED layer 17. Next, titanium, platinum, and titanium aredeposited in this order to form a barrier layer 15. Next, a materialincluding gold, such as pure gold, is deposited to form a buffer layer14 on the barrier layer 15. Next, a barrier layer 13 is formed on thebuffer layer 14. Next, a material including gold, such as pure gold, isdeposited to form a bonding layer 32 on the barrier layer 13. Thethickness of the bonding layer 32 is set to approximately half thethickness of the bonding layer 12 (see FIG. 1) in the completedsemiconductor light emitting element 1. Thus, an LED member 42 with theLED layer 17, the reflection layer 16, the barrier layer 15, the bufferlayer 14, the barrier layer 13, and the bonding layer 32 stacked in thisorder on the crystal growth substrate 30 is fabricated.

Next, as shown in FIG. 2C, on at least one of the bonding layer 31 andthe bonding layer 32, an indium layer 33 is formed. Then, the bondinglayer 31 of the support member 41 and the bonding layer 32 of the LEDmember 42 are brought into abutment via the indium layer 33 to stack thesupport member 41 and the LED member 42. At this stage, numerous voids(not shown) exist between the bonding layer 31 and the bonding layer 32.

Next, as shown in FIG. 3A, heat treatment is performed to melt theindium layer 33. Thus, the indium layer 33 is turned to liquid phase andfills the voids. Furthermore, indium atoms constituting the indium layer33 diffuse into the bonding layer 31 and the bonding layer 32 and reactwith gold atoms constituting the bonding layers 31 and 32 to form agold-indium alloy. Thus, the bonding layer 31 and the bonding layer 32are bonded via the indium layer 33 to constitute one bonding layer 12made of gold-indium (Au—In) alloy. In this process, the bonding layers31 and 32 made of pure gold are turned to the bonding layer 12 made ofgold-indium alloy. Thus, the bonding layer 12 is hardened, and itsviscosity is decreased.

However, at this time, indium atoms diffused into the bonding layer 32are blocked from diffusion by the barrier layer 13. This prevents theindium atoms from penetrating into the buffer layer 14 and reacting withgold constituting the buffer layer 14. Thus, the composition of thebuffer layer 14 remains pure gold. Hence, the buffer layer 14 is softerthan the bonding layers 31 and 32 after bonding, i.e., the bonding layer12 made of gold-indium alloy.

Next, as shown in FIG. 3B, the crystal growth substrate 30 (see FIG. 3A)is removed. Next, on part of the surface of the LED layer 17 having beenin contact with the crystal growth substrate 30, an upper electrodelayer 18 is formed. Furthermore, on the entire lower surface of thesupport substrate 10, a lower electrode layer 19 is formed. Next,sintering treatment is performed. That is, by heat treatment, the upperelectrode layer 18 is brought into ohmic contact with the LED layer 17,and the lower electrode layer 19 is brought into ohmic contact with thesupport substrate 10.

Next, as shown in FIG. 4, the stacked body fabricated as describedabove, i.e., the stacked body 43 made of the lower electrode layer 19,the support substrate 10, the barrier layer 11, the bonding layer 12,the barrier layer 13, the buffer layer 14, the barrier layer 15, thereflection layer 16, the LED layer 17, and the upper electrode layer 18is diced with a blade 50. The blade 50 is shaped like e.g. a disk, andlocally removes the stacked body 43 by rotation. As a result, thestacked body 43 is divided into a plurality of semiconductor lightemitting elements 1. Thus, the semiconductor light emitting element 1 ismanufactured.

Next, the operation and effect of this embodiment are described.

In the step shown in FIG. 2C, when the LED member 42 is placed on thesupport member 41, numerous voids occur between the bonding layer 31 andthe bonding layer 32. At this time, it may be considered that withoutproviding the indium layer 33, the bonding layer 31 and the bondinglayer 32 made of gold could be directly brought into abutment. However,in this case, because gold has low fluidity, even with the heattreatment shown in FIG. 3A, the voids are not eliminated but left in thebonding layer 12. This decreases the bonding strength.

Thus, in this embodiment, the bonding layer 31 and the bonding layer 32are brought into abutment via the indium layer 33, and then heated.Accordingly, the indium layer 33 is turned into liquid and flows to fillthe voids. That is, the bonding layer 31 and the bonding layer 32 can berobustly bonded by liquid phase diffusion bonding. However, the bondinglayer 12 is then turned to a gold-indium alloy and hardened.

In this embodiment, between the bonding layer 12 and the reflectionlayer 16, a buffer layer 14 being softer and having higher viscositythan the bonding layer 12 is placed. Thus, in the dicing step shown inFIG. 4, the buffer layer 14 can relax the mechanical stress and impactapplied to the stacked body 43. As a result, in the dicing step, peelingat the interface of any layer in the stacked body 43 can be suppressed.Thus, the semiconductor light emitting element 1 can be manufacturedwith high yield, and the cost can be kept low. In particular, by formingthe buffer layer 14 from gold, a buffer layer being particularly soft,having high conductivity, and being resistant to corrosion can berealized.

Furthermore, in this embodiment, a barrier layer 13 is provided betweenthe bonding layer 12 and the buffer layer 14. Thus, both in the bondingshown in FIG. 3A and in the sintering treatment shown in FIG. 3B, entryof indium atoms diffusing in the bonding layer 12 into the buffer layer14 can be suppressed. Hence, the buffer layer 14 can be kept in the softstate of pure gold. Furthermore, a barrier layer 11 is provided betweenthe support substrate 10 and the bonding layer 12, and a barrier layer15 is provided between the buffer layer 14 and the reflection layer 16.Thus, reactions between these substrate and layers can also besuppressed.

Next, a second embodiment is described.

FIG. 5 is a sectional view illustrating a semiconductor light emittingelement according to this embodiment.

As shown in FIG. 5, the semiconductor light emitting element 2 accordingto this embodiment is different from the semiconductor light emittingelement 1 (see FIG. 1) according to the above first embodiment in thatthe arrangement of the bonding layer 12 and the buffer layer 14 isreversed. That is, on the support substrate 10, a barrier layer 11, abuffer layer 14, a barrier layer 13, a bonding layer 12, a barrier layer15, a reflection layer 16, and an LED layer 17 are stacked in thisorder.

FIGS. 6A to 6C are process sectional views illustrating a method formanufacturing a semiconductor light emitting element according to thisembodiment.

First, as shown in FIG. 6A, on the support substrate 10, titanium,platinum, and titanium are deposited in this order to form a barrierlayer 11. Next, a material including gold, such as pure gold, isdeposited to form a buffer layer 14 on the barrier layer 11. Next, abarrier layer 13 is formed on the buffer layer 14. Next, a materialincluding gold, such as pure gold, is deposited to form a bonding layer31 on the barrier layer 13. Thus, a support member 46 with the barrierlayer 11, the buffer layer 14, the barrier layer 13, and the bondinglayer 31 stacked on the support substrate 10 is fabricated.

On the other hand, as shown in FIG. 6B, on the crystal growth substrate30, an LED layer 17 is formed. Next, silver, for instance, is depositedto form a reflection layer 16 on the LED layer 17. Next, a barrier layer15 is formed on the reflection layer 16. Next, a material includinggold, such as pure gold, is deposited to form a bonding layer 32 on thebarrier layer 15. Thus, an LED member 47 with the LED layer 17, thereflection layer 16, the barrier layer 15, and the bonding layer 32stacked in this order on the crystal growth substrate 30 is fabricated.

The subsequent manufacturing method is similar to that of the abovefirst embodiment. More specifically, the bonding layer 31 and thebonding layer 32 are brought into abutment via an indium layer 33. Next,gold included in the bonding layer 31 and the bonding layer 32 isreacted with indium included in the indium layer 33 to bond the bondinglayer 31 and the bonding layer 32. Thus, a bonding layer 12 made ofgold-indium alloy is formed. Next, the crystal growth substrate 30 isremoved. Next, an upper electrode layer 18 is formed on the LED layer17, and a lower electrode layer 19 is formed on the lower surface of thesupport substrate 10. Next, by heat treatment, the upper electrode layer18 is brought into ohmic contact with the LED layer 17, and the lowerelectrode layer 19 is brought into ohmic contact with the supportsubstrate 10. Then, the stacked body made of the support substrate 10,the barrier layer 11, the buffer layer 14, the barrier layer 13, thebonding layer 12, the barrier layer 15, the reflection layer 16, and theLED layer 17 is divided by dicing. Thus, the semiconductor lightemitting element 2 according to this embodiment is manufactured.

This embodiment can also achieve similar effects to those of the abovefirst embodiment. The configuration, manufacturing method, and operationand effect of this embodiment other than the foregoing are similar tothose of the above first embodiment.

Next, a third embodiment is described.

FIG. 7 is a sectional view illustrating a semiconductor light emittingelement according to this embodiment.

As shown in FIG. 7, in the semiconductor light emitting element 3according to this embodiment, the buffer layer 14 is provided in twolayers. The buffer layers 14 are placed between the support substrate 10and the bonding layer 12, and between the bonding layer 12 and thereflection layer 16. Furthermore, the barrier layer 13 is also providedin two layers. The barrier layer 13 is provided between each bufferlayer 14 and the bonding layer 12. That is, on the support substrate 10,a barrier layer 11, a buffer layer 14, a barrier layer 13, a bondinglayer 12, a barrier layer 13, a buffer layer 14, a barrier layer 15, areflection layer 16, and an LED layer 17 are stacked in this order.

This semiconductor light emitting element 3 can be manufactured asfollows. The support member 46 shown in FIG. 6A and the LED member 42shown in FIG. 2B are fabricated and bonded via an indium layer 33.Subsequently, an upper electrode layer 18 and a lower electrode layer 19are formed. Then, dicing is performed.

According to this embodiment, two buffer layers 14 are provided on bothsides of the bonding layer 12. Thus, interlayer peeling at the time ofdicing can be reliably prevented.

The configuration, manufacturing method, and operation and effect ofthis embodiment other than the foregoing are similar to those of theabove first embodiment.

Next, a fourth embodiment will be described.

FIG. 8 is a sectional view illustrating a semiconductor light emittingelement according to the embodiment.

As shown in FIG. 8, in the semiconductor light emitting element 4according to the embodiment, a conductive alloying suppression layer 48is provided between the reflection layer 16 and the LED layer 17 inaddition to the configuration of the semiconductor light emittingelement 1 (see FIG. 1) according to the above first embodiment. Theconductive alloying suppression layer 48 does not react to form an alloybetween the reflection layer 16 and the LED layer 17, and has astructure assuring an electrical conduction and preferably transmit thelight. The conductive alloying suppression layer 48 can be based on, forexample, an ITO (Indium-Tin-Oxide) layer.

In the embodiment, the conductive alloying suppression layer 48 isprovided, this can prevent formation of the alloying reaction layerbetween the reaction layer 16 and the LED layer 17 and reduction of thereflection efficiency due to conversion of this alloying reaction layerto a light absorption layer.

The configuration, manufacturing method, and operation and effect ofthis embodiment other than the foregoing are similar to those of theabove first embodiment.

Next, a fifth embodiment will be described.

FIG. 9 is a sectional view illustrating a semiconductor light emittingelement according to the embodiment.

As shown in FIG. 9, in the semiconductor light emitting element 5according to the embodiment, a current narrowing layer 49 is providedbetween the reflection layer 16 and the LED layer in addition to theconfiguration of the semiconductor light emitting element (see FIG. 1)according to the above first embodiment. The current narrowing layer 49is an insulating layer selectively placed in an arbitrary pattern on thecurrent path of the current supplied to the LED layer 17, for example,can be based on an electrically insulating layer made of a silicon oxidelayer or silicon nitride layer and the like.

In the embodiment, a current density of the current supplied to the LEDlayer 17 can be adjusted by providing the current narrowing layer 49.

The configuration, manufacturing method, and operation and effect ofthis embodiment other than the foregoing are similar to those of theabove first embodiment.

The position of the current narrowing layer is not limited to a positionbetween the reflection layer 16 and the LED layer 17, and may be aposition intervening on the current path of the current supplied to theLED layer 17. Both the conductive alloying suppression layer 48 (seeFIG. 8) of the above fourth embodiment and the current narrowing layer49 of the embodiment may be provided.

In the above embodiments, the bonding layers 31 and 32 are formed fromgold and bonded via an indium layer 33. Thus, the bonding layer 12 isformed from gold-indium alloy. On the other hand, the buffer layer 14 isformed from gold. However, the embodiments are not limited thereto. Thebuffer layer 14 achieves the effect of relaxing the stress associatedwith dicing as long as it is softer than the bonding layer 12 afterbonding.

Next, a comparative example is described.

FIG. 10 is a sectional view illustrating a semiconductor light emittingelement according to this comparative example.

FIG. 11 illustrates a method for manufacturing a semiconductor lightemitting element according to this comparative example.

As shown in FIG. 10, the semiconductor light emitting element 101according to this comparative example does not include the buffer layer14 (see FIG. 1). Furthermore, the barrier layer 13 (see FIG. 1) betweenthe bonding layer 12 and the buffer layer 14 is also not provided.

As shown in FIG. 11, in manufacturing such a semiconductor lightemitting element 101, in the dicing step, peeling often occurs at one ofthe interfaces. In particular, peeling frequently occurs at theinterface with low degree of contact, such as the interface between thesupport substrate 10 and the barrier layer 11, and the interface betweenthe barrier layer 15 and the reflection layer 16, which aresemiconductor-metal interfaces. The reason for this is considered asfollows. Because the buffer layer 14 is not provided, the mechanicalstress associated with dicing is not relaxed. The stress concentrates onthe weakest portion in the stacked body. As a result, the semiconductorlight emitting element 101 has low yield, and the manufacturing cost isincreased.

The embodiments described above can realize a semiconductor lightemitting element and a method for manufacturing the same in whichpeeling is less likely to occur in the dicing step.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A semiconductor light emitting elementcomprising: a support substrate; a first metal layer provided on thesupport substrate; a bonding layer provided on the first metal layer,the bonding layer consisting of an alloy containing a first componentand a second component; a second metal layer provided on the bondinglayer; an LED layer provided on the second metal layer; and a bufferlayer containing the first component, the buffer layer being softer thanthe bonding layer, each of the first metal layer and the second metallayer including: a layer containing titanium, and a layer containingplatinum; and the buffer layer being placed in one of between thesupport substrate and the first metal layer and between the second metallayer and the LED layer.
 2. The element according to claim 1, furthercomprising another buffer layer placed in the other of between thesupport substrate and the first metal layer and between the second metallayer and the LED layer, and the another buffer layer being softer thanthe bonding layer.
 3. The element according to claim 1, furthercomprising a reflection layer placed between the LED layer and thebuffer layer and between the LED layer and the bonding layer.
 4. Theelement according to claim 3, wherein the reflection layer containssilver.
 5. The element according to claim 3, further comprising aconductive alloying suppression layer provided between the reflectionlayer and the LED layer, not reacting to form an alloy between thereflection layer and the LED layer, and being conductive.
 6. The elementaccording to claim 1, further comprising an insulating current narrowinglayer selectively placed on a current path of a current supplied to theLED layer.
 7. The element according to claim 1, wherein the firstcomponent is gold, and the second component is indium.
 8. Asemiconductor light emitting element comprising: a support substrate; afirst metal layer provided on the support substrate; a bonding layerprovided on the first metal layer, the bonding layer consisting of analloy containing a first component and a second component; a secondmetal layer provided on the bonding layer; an LED layer provided on thesecond metal layer; and a buffer layer containing the first component,the buffer layer being softer than the bonding layer, each of the firstmetal layer and the second metal layer including: a layer containingtitanium; and a layer containing platinum, the buffer layer being placedin one of between the first metal layer and the bonding layer andbetween the bonding layer and the second metal layer.
 9. The elementaccording to claim 8, further comprising another buffer layer placed inthe other of between the first metal layer and the bonding layer andbetween the bonding layer and the second metal layer, and the anotherbuffer layer being softer than the bonding layer.
 10. The elementaccording to claim 8, further comprising a reflection layer placedbetween the LED layer and the buffer layer and between the LED layer andthe bonding layer.
 11. The element according to claim 10, wherein thereflection layer contains silver.
 12. The element according to claim 10,further comprising a conductive alloying suppression layer providedbetween the reflection layer and the LED layer, not reacting to form analloy between the reflection layer and the LED layer, and beingconductive.
 13. The element according to claim 8, further comprising aninsulating current narrowing layer selectively placed on a current pathof a current supplied to the LED layer.
 14. The element according toclaim 8, wherein the first component is gold, and the second componentis indium.